Proteomics Analysis On Chloroplast Of Cassava(Manihot Esculenta Crantz) Under Different Light Conditions

As a typical tropical and subtropical crop, cassava (Manihot esculenta Crantz) has the C4-like structure, high net photosynthetic rate, high Photosynthesis efficiency, and its physical and chemical properties of Photosynthesis is superior to other crops. However, its mechanism of high photosynthesis is still unknown. Studying on the mechanisms of high photosynthesis efficiency and photosynthesis process in cassava can not only enrich the theory of cassava research, but also provide a theoretical basis for cassava breeding and germplasm screening. This study chosed cassava SC8as test material, and analyzed the differentially expressed proteins of its chloroplast under the control check, continuous light and dark condition by comparative proteomics and phosphorylated proteomics technology. The study investigated the pathway and mechanism of high photosynthesis efficiency of the SC8cassava. The main results were as follows:1. The change tendency of content of chlorophyll soil and plant analyzer development (SPAD) ratio, malondialdehyde (MDA), proline, soluble sugar, starch in one, three, five day after treatment were the same under continuous light and dark condition, but amplitudes were different. What the content of MDA increases suggested that the membrane lipid peroxidation was happened.2. The change tendency of activity of Superoxide dismutase (SOD), Peroxidase (POD), Ascorbate peroxidase (APX) and Catalase (CAT) on one, three, five days after treatment was the same under continuous light and dark condition.Up-expression of SOD and CAT suggested that they may be main role in antioxidant protection mechanism.3. A total of195differentially expressed protein spots from chloroplast of cassava were screened out, among them,175protein spots were successfully identified by MALDI TOF and MALDI TOF-TOF, corresponding to122differentially expressed proteins, which106proteins were from continuous light condition,121proteins were from dark condition.4. The change tendency of expression quantity of122differentially expressed proteins indicates that the amount of down-expression protein was greater than the amount of up-expression protein. There were five types of protein expression changes between differentially expressed proteins under continuous light and dark condition.5. Analysis of Gene Ontology (GO) showed that the distribution of122different proteins invovled in cell competent, molecular function, biological process were same. In cell competent, most proteins were in thylakoid membrane, account for26%and27%of total differentially expressed proteins under the continuous light and dark condition, respectively. In molecular function, those identified proteins involved ion binding, nucleoside binding and nucleotide binding were the most, account for26%,24%and25%, respectively. In biological process, most proteins participated in cellular metabolic process and primary metabolic process, account for55%and45%, respectively.6. Metabolic pathway that122differentially expressed proteins involved was analyzed by using KOBAS2.0. We found83pathways during searching database, including31KEGG pathway, as among them, photosynthesis, oxidative phosphorylation, Photosynthesis-antenna proteins, glyoxylate and dicarboxylate metabolism, carbon metabolism pathways were presented enrichment and suggested an important role in the process of high photosynthetic efficiency in cassava.7. The expression level of seven differentially expressed proteins glutamine synthetase leaf isozyme precursor (GS), phosphoglycerate kinase (PGK), triosephosphate isomerase (TPI), oxygen-evolving enhancer protein (OEE), carbonic anhydrase(CA), phosphoribulokinase (PRK) and photosystem ? stability assembly factor HCF136(PS? HCF136) were compared in mRNA and protein levels respectively. PGK, CA and PS? HCF136were consistent, and TPI was opposite under continuous light condition; GS was consistent, and TPI and CA were opposite under dark condition. It indicates that expression change of most proteins was different in mRNA and protein levels.8. Twenty two differentially expressed c proteins were identified by phosphorylated proteomics, corresponding to20proteins from the122proteins. GO Analysis showed that most proteins located in membrane structure and oxygen evolving complex with ion binding and ATP bind function, and involved in Photosynthesis and photosynthesis-antenna.9. We cloned the full-length genes of OEE, PRK, PSII HCF136and PGK gene by RACE method, and carried out sequence analysis and bioinformatics analysis, respectively.In conclusion, these results could be shed light on the mechanism of high photosynthesis efficiency, also to provide some basic information for the future molecular improvement and high photosynthetic efficiency breeding of cassava.